The present invention relates to an electronic apparatus, such as an electronic cash register (hereinafter called ECR) that registers and processes a variety of trade data, or a "teller machine"- normally used to process bank data. The present invention relates more particularly to the method of modifying programs stored in an ECR. The system simply and easily implements needed changes or modifications of programs related to the processing of a variety of trade data stored in the stationary memory.
In conventional ECRs, a low cost stationary mask ROM (read-only memory) is used to store a variety of programs related to the processing of trade data. However, the programs become stationary after they have been written into the mask ROM. In practice, there are many cases which require that part of the processed program be changed or modified after the processed program is stored in the mask ROM. Since the needed program was already stored, it was necessary to replace the mask ROM with a new one in order to change or modify the contents. As a result, to either change or modify the needed program, it is not only expensive but also time and labor consuming.
In light of the disadvantage described above, (as officially disclosed by Japanese Patent Application No. 72301 of 1982), the inventors proposed an art in conjunction with the method of writing and storing a variety of specific data needed to modify programs stored in an ECR's mask ROM by applying the following memory means; a second memory containing addresses identical to those in the mask ROM which serves primarily as the first memory; a third memory storing the data denoting addresses of the programs that require modification; a fourth memory storing modified programs; and a means for entering and processing a variety of trade data using an ECR's mode-select means of selecting a specific mode without providing the means of writing programs independent of the ECR.
Nevertheless, the proposed system still had disadvantages: to independently store data into the third and fourth memories involved complex operations for writing data including the data for the modified programs. In addition, there was a certain limit to the total volume of the modified programs as restricted by the capacity of the third memory.